1. Field of the Invention
The present invention is directed to a fastener from which objects can be hung. It is particularly directed to a self-drilling fastener to be used in a friable material such as drywall, in drywall mounted to a member or in thin rigid or semi-rigid materials such as hollow-core doors.
2. Description of the Related Art
Because drywall is a friable material, mounting articles thereto can be difficult. In the past, at least three methods have been used. For light weight articles, small plastic expansion anchors have been used. These expansion anchors have typically required three steps to install: first, a hole is drilled into the drywall; second, the drywall fastener insert is driven into the drilled hole; and finally, a threaded fastener is advanced into the drywall fastener, spreading the drywall fastener into engagement with the drywall. However, expansion anchors can typically hold light loads only.
For heavy duty applications, toggle bolts have been used. While toggle bolts have been effective, they are also generally expensive because they involve parts which must move relative to one another. Toggle bolts also have been known to be difficult to install.
Self-drilling anchors for mounting heavier loads also have been used. These self-drilling anchors typically are installed by drilling into the drywall with the drywall fastener itself. The drywall fastener also includes threading having a high thread height to provide a high pullout in the drywall. Examples of self-drilling anchors include the drywall fastener sold under the trademark E-Z ANCOR manufactured by ITW Buildex, and those disclosed in U.S. Pat. Nos. 4,601,625, 5,190,425, and 5,558,479, all of which are assigned to the assignee of this application.
Self-drilling anchors have proved effective for holding higher loads when installed in drywall alone. However, in most cases the drywall is mounted to wood support members, or studs, that are unseen by the user, and typically the location of these support members are unknown and unchecked by the user. When a user of a typical self-drilling fastener attempts to install the drywall fastener in drywall at a location of a support member, the drywall fastener is unable to drill into the support member, causing the drywall fastener to spin in place so that the drywall fastener's high threading strips out the drywall, resulting in failure of the drywall fastener and creating an unsightly scar on the wall. Even if the drywall fastener is able to drill into the support member slightly, the anchors have been known to tightly engage the support member and break due to torsion on the anchor.
Mounting self-drilling fasteners to relatively thin semi-rigid materials such as a veneered panel of a hollow door can also be difficult. The small thickness of the material and the splintering caused during driving may significantly reduce the holding strength of the fastener.
In many of these cases, the head of the fastener seats flush with the mounting surface, preventing a user from hanging an object from the fastener. In order to remedy this situation, a user may not install a fastener fully, leaving a portion of it protruding from the wall. In this instance, the threads of the fastener may not be engaged fully with the mounting surface, thereby weakening the holding capability of the fastener.
What is needed is a self-drilling fastener that can be installed either in drywall, in drywall and a support member or in a rigid or semi-rigid material and is capable of handling a heavy load.